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Full text of "Text Book Of Mechanical Engineering"

Bearings.

235

XVII. Crank Shaft Bearing (Fig. 248). The bearing
is first'laid level on its side as at B, the centre line obtained,
and scribed -round. The seatings for the brasses are measured
and also scribed, after which the bearing is set up as at c (see
both views), and adjusted by line and square till plumb. The
foot is next lined, and the top of the bearing taken from this,
making sure that there is sufficient stuff left in the bush socket.
Now plane in turn the seating sides, the foot bottom, and the
top. Stand the casting again on the marking table as at D, and
find the centre of the socket. Square this up, as well as the
socket sides. Scribe the bottom of the socket, measuring from
the foot, and line the bearing centre all round. Square these
lines across as in plan at E, and mark them on the opposite side.
Find the centre of the set screw-holes, and measure the foot bolt-
holes from the vertical centre line. Plane out the bush socketó
the sides with a side tool, and the bottom with a front tool,
finishing with a flat tool, and the corners with the ' corner' tool
shewn at F. Drill the holes.

The Cap or 'keep' is set on edge to line the seatings and
scribe the two bolt-holes and oil-holes, as at G, being first, how-
ever, planed to thickness on its bottom surface. After planing
also the seatings, and drilling the holes, it is'placed in position
on the top of the bearings, and the bolt-holes marked through to
the latter. These are next drilled and tapped, and the studs put
in place.

The Brasses are shewn in Fig. 249. Being first laid on its
side, as at A, the large brass has its width marked and its lips
lined for thickness, and is then planed. The front and sides are
next lined out on*all surfaces to dimensions, measuring from the
planed surface, and trying for depth of stuff between the lips, the
brass being meanwhile packed with sides truly vertical, as at B.
The whole is now planed by clamping in the successive positions,
c, D, and B, so that every surface is done, either with a side or front
or knife tool, the depth of the middle surface being gauged from the
lip; and the small brass F is similarly treated. (SeeApp. /.,/. 752.)

The packing plates are next machined, and all is ready to put
together. The brasses and packing are to be carefully smooth-
filed and scraped until they bed perfectly into their places in the